Alternating pulse servo system



9, 1960 w. LEATHERS EI'AL 2,948,193

ALTERNATING PULSE SERVO SYSTEM Filed Sept. 8, 1953 6 Sheets-Sheet 1ELEvATION sERvO MECHANISM TRAv RsE sERvO MECHANISM 12 6 6 17 r ELEVATIONTANK TRAVERSE CTRLHANDLE ENGINE CTRL.HANDLE 7 I O PCK FF PICKOFF ALT.PULSE ALT. PULSE I 1I/ GENERATOR GENERATOR PRI. VALVE PRI. vALvE CONTROLHYDRAULIC CONTROL UNIT POWER UNIT 1 r 1 SUPPLY L8 I 8 SEC. VALVE i sEC.VALVE I l a 5 3 a N0 o MANUAL" BACK I HYDRAULIC g L MOTOR LL sELEcTOR \9VALVE GEAR BOX T s ELEVATION NO I 3 CYLINDER MANUAL BACK I TURRET 10 10f GUN b III } INVENTORS WARD LEATHERS FRANK J. FURMAN HUGO A.PANISSIDIATTORNEY HUGO A. PANISSIDI 7 EA) M ATTORNEY ALTERNATING PULSE SERVOSYSTEM Aug. 9, 1960 Filed Sept. 8, 195a Aug. 9, 1960 Filed Sept. 8, 1953w. LEATHERS ETAL ALTERNATING PULSE SERVO SYSTEM 6 Sheets-Sheet 3 FIG. 3

RESERVOIR I N I E NTORS WARD LEATHERS FRANK J. FURMAN HUGO A PANISSlD!NMX M ATTORNEY Aug. 9, 1960 w. LEATHERS EIAL 4 ALTERNATING PULSE SERVOSYSTEM Filed Sept. 8, 1953 6 Sheets-Sheet 4 1 NIE N TORS WARD LEATHERSFRANK J. FURMAN HUGO A. PANISSIDI BY VYX M A TTOR NE Y Aug. 9, 1960 I w.LEATHERS ETAL 2,948,193

ALTERNATING PULSE SERVO SYSTEM Filed Sept. 8, 1953 e Sheets-Sheet 5 1NVE N TORS WARD LEATHERS FRANK J. FURMAN 359 HUGO A. PANISSIDI 358 JBYE-# 4) ATTORNEY Aug. 9, 1960 W. LEATHERS ETAL ALTERNATING PULSE SERVOSYSTEM Filed Sept. 8, 1953 6 Sheets-Sheet 6 IN V EN TORS.

WARD LEATHERS FRANK J. FURMAN HUGO A. PANISSIDI ATTORNEY Patented Aug.9, 1960 2,948,193 ALTERNATIN G PULSE SERVO SYSTEM Ward Leathers,Brooklyn, Frank J. Furman, Endicott, and

Hugo A. Panissidi, Binghamton, N.Y., assignors to International BusinessMachines Corporation, NewYorlr, N.Y., a corporation of New York- FiledSept. 8, 1953, Ser. No. 378,696

Claims. (CI. 89-41) This invention deals with an improved gunstabilization and control system of the hydraulic type with automaticelectric control of the hydraulic system as well as a manual controlsystem.

More specifically, this application is a continuation in part ofapplication, Ser. No. 284,606, filed April 26, 1952, and assigned to theUnited States of America.

An object of this invention is to provide an improved gun stabilizationand control system for use with a gun mounted on a moving vehicle, suchas a tank.

Another object is to provide a control system for a gun, which systemhas safety features to guard against damage to personnel as well asdamage to the mechanism.

A further object of this invention is to provide an electric controlcircuit which has elements that cooperate with hydraulic elements of thegun stabilization and control system to produce a superior system whichis best adapted to control a, turret mounted gun on an armored vehiclesuch as a tank.

These and other objects will appear more fully in the detaileddescription which follows, and in the drawings in which:

Fig. 1 is a block diagram of the complete traverse and elevation servocontrol systems of this invention showing the functional relationship ofall the elements involved;

Fig. 2 is a schematic diagram showing the physical relation of theelements, especially the gyroscopes and the gun, to clarify theembodiments of the differential mechanism of each servo system;

Fig. 3 is a schematic diagram of the hydraulic supply system located inthe hull of the tank for the improved control system of this invention;

Figs. 4a and 4b together constitute a schematic layout ofthe improvedsystem of this invention located in the turret;

Fig. 5 is an electrical circuit diagram of the electric control systemof this invention; and

Fig. 6 is an enlarged detail showing the hydraluic no-back device inproper proportions.

The basic elements of the system of this invention are best explainedwith reference to a block diagram such as that illustrated in Fig. 1.The system includes three :basic functions, namely; onegun stabilizationand tracking by means of two independent servo mechanisms 1 and 2;two-manual gun control whereby the gun may be positioned in either theelevation or traverse plane by :hand driven mechanisms 3 and 4;threetravel lock "whereby the gun and turret will be automaticallylocked to the tank hull when the stabilizer or hand driven mechanismsare not in use, such travel lock being accomplished by no-backs 5, usedin conjunction with the hand driven mechanisms 3 and 4. r p In order tostabilize the gun in both the elevation and traverse planes with respectto a celestial line of reference, it requires two independent servomechanisms 1 and 2 as shown in Fig. 1, each servo system comprisingagyroscope 6 to establisha mechanical celestial line of ranged to eitherreposition the gun at a relatively slow reference, a sensing device 7for the servo mechanism to detect any angular variations from thegyroscopic line of reference, a controlling unit 8 which controls powerto a prime mover as a function of these angular variations, and finallya follow-up 9 from the load 10 of the prime mover to the sensing device7 through a mechanical differential 11 to complete the servo loop. Theother input to the mechanical diiferential 11 is from the gunners orcommanders tracking handles, 12.

The purpose of the stabilizer and tracking systems is to keep the gunstabilized with respect to the gyroscopic line of reference regardlessof vehicle motion over reasonably rough terrain and at the same timeallow the gunner or commander to vary the position-of the sensingmechanism 7 with respect to the gyroscopic line of reference in order totrack the gun with a moving target or correct for parallax or positionthe gun to a new target ly in traverse, it becomes impossible tomaintain any good accuracy of fire while the tank is in motion. This istrue of a target which is stationary and doubly true when a target isalso in motion.

, Stabilization of a gun in a moving vehicle is possible only when thesystem employs a celestial line of reference, i.e., maintains theorientation of the gun constant with respect to space.

When a tank is traveling in some line other than directly toward thetarget then parallax will be introduced, therefore, some provision mustbe made for manually operating the power control to track the gun inboth elevation and traverse to effect correction for deviationintroduced by parallax. Another reason for being able to reposition thegun by tracking is that often the target itself may also be moving.Also, it may be desired to change from one target to another which maybe at a considerably different elevation or angle of traverse from theinitial target. These various conditions dictate that supplementalmanual power controls be provided to enable the gunner to rapidlyreposition (or track) the either in elevation orv traverse or both. Suchtracking controls are also aror at relatively more rapid rate dependingupon the extent of manual adjustment. As will appear in the detaileddescription of the system, such tracking control is intro duced bymanual control handles in conjunction with electric motors, forrepositioning the pick-off mechanism of the gyroscopes which aremaintaining the gun stabilized about the two axes mentioned, i.e., intraverse or azimuth and in elevation.

There are two separate servomechanisms involved, one of which controlsthe position of a gun in elevation and the other controls a turret whichpositions the gun in traverse. Generally, each servomechanism comprisesa pick-01f mechanism providing alternate timed pulses, the timedduration of which is determined in accordance with the deviation of theposition of the gun from the gyroscopic line of reference. Thealternating pulses vary in time duration and are complementary to oneanother, i.e., as one pulse increases in time duration, the opposite andnext succeeding pulse decreases proportionately in time duration.

These pulses are directed to a controlling unit which generallycomprises an electrodynamically actuated primary valve converting theelectrical pulses into correspond ing hydraulic pulses. These hydraulicpulses arein turn The result is that,.if the gun. which is carried bythe tank is not well stabilized, especialamplified by a secondary valvestructure which is actuated by the hydraulic pulses from the primaryvalve.

The amplified hydraulic pulses, which are alternating in character andvariable in time-duration as a function of angular error of the gun withrespect to the gyroscopic line of reference, are. applied to a hydraulicprime mover which serves to actuate or stabilize the or turret.

A follow-up device is provided to link the gun with the pick-offmechanism through a differential. The other input to the differential isprovided from the control handles. Consequently, aiming of the may becornpletely controlled in both elevation and traverse. Since the gun maybe mounted in abalaneed state, itselev ation position may becontrolledby asingle hyd aulic cylinder and piston, whereasflto controlthe turret in traverse involves the moving of the turret itself and alsothe gun which is mountedon the turret. Naturally, the turret will bemounted in' good anti-friction bearings,'but the great mass involved inthese very heavy parts means that a heavy duty drive mechanismisnecessary to control the turret in traverse. i

Fig, 2 shows schematically the relationsof the various elements of thetwo servo systems involved. An important feature in the understanding ofthe operation of these servo systems is the differential, which in factis the means by which tracking is superimposed upon mere stabilizationcontrol. Any suitable mechanical differential means might be employedbut a very simple and reliable one has been used, which eliminates anyneed for a remote connection between the gun and the pick-off mechanismselements. This means used is simply that of mounting each of the twogyroscopes directly on the gun with its stable axis properly aligned forstabilizing about the elevation and traverse axes. For example, note theelevation gyroscope unit 370-which is mounted on the side of the gun 44.The gym unit 370 has a turntable 265 which has the gyroscope and itsrelated pick-off elements mounted thereon. The details of these elementshave been described with more particularity in application, Serial No.284,606, previously referred to. It is suificient to point out here thatthe gyroscope acts to hold a pickoff contact (not shown) in a constantposition relative to space. Therefore, if the turntable 265 is rotatedabout its axis (which is parallel to the trunnion axis of the gun) anerror signal will be introduced into the elevation servo system andcorrection for this error will be made by the elevation cylinder 43. Nowattention is directed to the fact that turntable 265 may be rotated intwo ways; oneby rotation of the gun aboutits trunnions which carries thewhole gyro unit 370 and turntable 265 contained therein withit; andtwo-by rotation of-the turntable alone by means of a turntable motor 137which is mounted on the gun with gyro unit 370. It is these wo ways ofrotatin. the turntable which constitute the two inputs of adifferential, the output of which is the rotation or non-rotation ofturntable 265. By way of illustration of the differential action,suppose turntable motor 137 is energized and so the turntable 265 isrotated. An error signal will be set up by the pick-off elements in aknown manner such as that described in the aforementioned application,Ser. No. 284,606, and so the gun will be rotated about its trunnion axisby the cylinder 43. This rotation of the gun will be in the oppositedirection from that taken by the turntable 265 and will tend to returnthe turntable to its original position or at least stop its initialrotation so that the gun will continue to rotate as long as theturntable 265 is being driven by its motor 137. This is the situationwhen tracking is being introduced. When stabilization alone is beingeffected, rotation-of th gun about its trunnion axis will rotate theturntable 265 with it, and this will cause an error signal to be set upas before. In this case, the error signal will cause the servo systern(by-nieans of the cylinder 43) to return the gun to its originalstabilized position as determined by the gyro maintained position of theturntable 265.

The same action takes place about the traverse axis 373 anda pair. ofpinions 374 to an internal ring gear 47 located on the hull of the tank.In this manner.

360 of rotation in traverse, may behadl.

In Figs. 3, 4a and 41 there is shown the system according to thisinvention whieh emhodies some 1mproved elements but which employs thesame basic alternate timed pulse stabilization and control system, asthat disclosed in application Ser. No. 284,606 mentioned above, butwhich is not per se involved in this invention. To describe this systemwe may begin with a description of the hydraulic pressure supplysystemas illustrated in Fig. 3. An engine 280; is the main engine for drivingthe tank. It has a take-off to a hydraulic fluid pump 281 by means of aclutch 282. This clutch may be any desired type which is adapted to beoperated hydraulically. Apreferred type of clutch is that shown whichconsists of the ordinary disc type Clutch. Ithas a drum member 233 whichis driven by a shaft 284 taken from the tank engine 280. The drum member283 is carried in bearings as shown and carries with it two discs 285and 286. These discs are splined to drum member ZSS for positiverotation therewith. A third disc member 287 is splined to an outputshaft 288 of the clutch. The shaft 283 is carried in appropriatebearings as shown and is coupled to the hydraulic pump in an appropriatemanner. The clutch 282 is actuated by means of an annular ring typepiston 289 which is carried in an annulus 290 and may slide laterallytherein. The ring 289 carries appropriate seals as illustrated and isactuated to slide laterally by means of hydraulic fluid introducedthrough hydraulic pipe 305. When hydraulic pressure is introduced intothe annulus 290 from hydraulic pipe 305, ring 289 is forced to the rightas shown in Fig. 3 and, therefore, applies lateral pressure by means ofbearings 306 to the discs 286, 287 and 285. Such lateral pressure on thediscs forces them into frictional engagement since they may slidelaterally on their splines, and such frictional engagement produces adirect coupling from engine shaft 28,4 to clutch output shaft 288 in theordinary manner of a disc type clutch.

Operation of the clutch is controlled by means of an electricallyactuated hydraulic valve 307. This valve consists of a ball 308 which isspring biased into the position shown by means of a rod 309 and a spring325. There is a guide (not shown) to keep the ball in line with the rod.When the ball is held in the position shown, it closes hydraulic inputpipe 326 which is connected to the main pressure line 338 of thehydraulic system. Under such conditions, no hydraulic pressure isapplied via pipe 305 to annulus 290 for operation of the clutch andtherefore the clutch is allowed to remain disengaged, In order to engagethe clutch, there is a solenoid 327 which actuates an armature 328carried by the rod 300. When the solenoid 327' is energized, it drawsarmature 328 to the right against the spring pressure of spring 325, andat the same time draws rod 309 to the right allowing ball 308 to beunseated and seated again on the aperture 329 to cause the fluidpressure to be applied directly to hydraulic pipe 305. and thence toannulus 290 and so actuate the clutch. Solenoid 327 is actuated by meansto be laterdescribed so that the, clutch may be actuated at appropriatetimes. The main purpose for having the clutch is to allow starting ofthe engine without the extra load of the hydraulic pump. Furthermore,this arrangement avoids driving the pump when dry (because no hydraulicpressure would then be available to actuate the clutch 282) which wouldbe very injurious-to the pump. There is a hydraulic pipe 330 which isconnected to the inside of valve 307 asshown in order to bleed oflhydraulic pressure from the clutch whenever ball 308 is seated againstthe inlet from pressure pipe 326. The remainder of the hydraulic systemshown is conventional. Pump 281 receives hydraulic fluid from areservoir 331 by means of hydraulic pipe 332 and forces hydraulic fluidunder pressure out through hydraulic pipe 333 and a filter shown to acheck valve 334 and then to a pressure regulator 335. The pressureregulator has connections in the conventional manner to pressure andreturn by means of hydraulic pipes 336 and 337 respectively. Pressurepipe 338 leading from the pressure regulator joins pipe 339 which isconnected to a hydraulic slip ring device 271, the lower portion ofwhich is here illustrated. There is an accumulator 363 which isconnected to the pressure side of the system in conventional manner.There is a relief valve 364 connected across from pressure to return asillustrated. Hydraulic fluid return comes from slip ring device 271 tohydraulic pipe 365, which leads to the reservoir 331 as illustrated.There is an oil-level-temperature switch 376 located in the reservoir331; The function of this oil-level-temperature switch in the system isas the name implies and will be explained more fully in connection withthe electrical circuit diagram of Fig. 5.

The remaining portion of the hydraulic system is shown in Figs. 4a and4b. Fluid under pressure is 'introduced from pressure pipe 339 (Fig; 3)to hydraulic slip ring device 271 (Fig. 4a). Fluid is then carriedthrough and sent to hydraulic pipe 272 under pressure as deter-- minedby the system pump 281 (Fig. 3) which is located in the hull. Pipe 272leads to a shut-off valve 273 which energizes the whole control systemwhen it is open.

Shut-01f valve 273 is controlled electrically from control box 274 bymeans of a solenoid 275. It may be observed that main valve core 276 iscontrolled by a differential of hydraulic forces. Its operation will beclear upon inspection of the drawing when it is pointed out that whenthe solenoid 275 is energized, the combination armature and rod 277 willpush the ball 279 from a'return valve seat 279a (as shown) to a pressureseat 27%. This then cuts off system pressure from the backor large areapiston integral with valve core 276, so that systempressure opens thevalve and holds it open. If, however, the solenoid 275 is deenergized,the ball 279 is allowed to rise off its pressure seat 27% and to seatitself on the return seat 2790:, as shown, with the aid of a spring275a; and then system pressure will be introduced into the auxiliarypassage so that the large area piston shown will force the valve core tothe left, as shown, and close the valve shutting olf the system pressureat this point.

With shut-off valve 273 energized, hydraulic fluid under pressure isintroduced in pipe 291 and so carried to pipe 292. This pipe 292 has afilter 293 for the traverse control system which is illustrated in Fig.4a. On the other side of filter 293, hydraulic pipe 294 leads to acontrol unit 295 which contains a primary valve 296, a secondary valve297, and an output bypass valve 298. Primary valve 296 is electricallyoperated by the coils 378 to reciprocate horizontally (as viewed in Fig.4a) in a square wave mechanical motion, as was generally described aboveand was described in detail in previously mentioned application, SerialNo. 284,606. The bypass valve 298 is pressure operated such that, ifsystem pressure falls below a predetermined value, the valve will open,while pressure above the value determined by a spring 300 will keep thevalve closed and allow fluid to be transmitted .to a hydraulic motor 299for operation of the same. The operation of this bypass valve willbeclear upon inspection. A rod 301 is snugly fitted in a passage shownwhich .is directly connected to system pressure. This rod 301 isintegral with a valve core 302 which seats on a passage 303 in order toisolate the two pressure lines shown which lead to hydraulic motor 299;If pressure falls below the predetermined level, spring 300 will actagainst a piston 3tl4which is attached to the valve core 302 and willopen the valve and create a bypass. The purpose of this bypass valve isto provide conditions such that when manual operation is eflfected,fluid circulated by the motor 299 (acting as a pump) can freely flow andthe resistance to manual operation will be low. Hydraulic motor 299drives the turret in traverse through a gear box 311, the details ofwhich form no part of the present invention per se.

Traverse gyroscope unit 312 can be a conventional gyroscope and pick-oflso long as the pick-off is a type which produces alternate timed pulsesas generally described above, in order to gain the benefits of analternate pulse servo system such as the basic servo system disclosedand claimed in the application, Serial No. 284,606. The gyroscope unitis electrically connected to the rest of the system as is indicated inFig. 4a, the electric circuit being shown in Fig. 5. There is acommanders handle and control box 313 which is arranged to take overmanual control from the gunners control station 314 (Fig. 4b) byelectrical means which will be fully described in connection with Fig.5. I

The elevation control system is shown in Fig.'4b where its operation maybe traced by following first the hydraulic pressure pipe 292 which leadsto a filter 315. From this filter 315, we may follow pressure pipe 316via flexible connector 317 and hydraulic pipe 318, to an elevationcontrol unit 319. This unit contains a primary'valve 320, and asecondary valve 321, like those of the traverse unit 295. This unit alsocontains a selector or changeover valve 322 which operates automaticallyby means of system pressure to selectively connect either theautomatically controlled primary and secondary valves 320 and 321 or toconnect a manual hydraulic pump 323, to the gun elevating cylinder 340.The details of this selector or changeover valve 322 are evident uponinspection'of Fig. 4b and are as follows: inner poppet valves 380 andouter poppet valves 381 are actuated by means of a piston operated cammember 383. All four poppets 380 and 381 are biased against the cammember 383 by springs 384. Cam member 383 has a compression spring 385,which biases the cam member to the left (as viewed in Fig. 4b), butwhich is overcome by system hydraulic pressure whenever it is at orabove a working pressure which may be predetermined by the stiffness ofspring 385. Now it will become apparent that the selector or changeovervalve 322 operates when system hydraulic pressure falls below a givenworking level to reverse the positions of inner and outer poppet valves380 and 381. This reversal takes place by the cam action when cam member383 'is moved to the other end of the cylindrical chamber in which it islocated, under the force of compression spring 385. So that, so long assystem hydraulic pressure is maintained, selector or changeover valve322 will remain in the position illustrated in Fig. 4b with cam member383 at the right end of its travel and with inner poppet valves 380open. This makes a hydraulic connection between gun elevating cylinder340 and secondary control valve 321 so that the elevation system is onautomatic stabilization or tracking control. On the other hand, ifsystem hydraulic pressure should fall below the predetermined workinglevel, cam member 383 would be moved over'to the left (as viewed in Fig.4b) under the force of compression spring 385, and so inner poppetvalves 380 would be closed and outer poppet valves 381 would be openedwhich would disconnect the primary and secondary control valves 320, 321and would connect hydraulic pipes 358 and 359 (of the manual elevationcontrol system to be described below) to the gun elevating cylinder 340for manual control of the gun elevation. Hydraulic passages of theelevation control unit 319 will not be traced-in detail; it issuflicient to note that there is'a piston 387 at the left end of cammember 383 (as viewed in Fig. 4b) which pistonhas the necessary rings orother type of seal to maintain the pressure of the hydraulic fluid which7 is introduced into a chamber 388 directly from pressure hydraulic pipe318.

Gun elevating cylinder 3401s an improved type. The details of thiscylinder form no part of the present inv'ention per se, but are thesubject matter of a separate application in the name of Lawrence BruehlSerial No. 340,451, filed March 5, '1953. Hydrauliciluid is intro ducedto either side of a piston 341, which has a piston rod 342 extendingfull length of the cylinder above and below the piston 341 -in order toequalize the effective pressure areas. There is a bleed passage 3d?)which operates to vent the space between a pair of hydraulic seals 341aand 341k encircling the piston 341; thereby preventing a pressure lockfrom developing between the seals rendering them useless, and at thesame time permitting the hydraulic seals 341a and 34% to be preloadedwhen pressure is applied to both sides of the piston as in the case ofmanual operation. The cylinder 340 is fastened securely to the. gun bymeans of a gimbal arrangement, only part of which is shown, for clarity.Lugs 344 are securely fastened so as to be integral with the top of thecylinder 340. These lugs 344 are in turn carried .by a gimbal ring 345which has lugs on it (not shown) at right angles to lugs 344. The lugs(not shown) on gim'bal ring 345 are in turn carried by brackets (notshown) which are fastend to the gun. At the lower end, piston rod 342has an eye bracket 346, which maybe used to fasten the piston rod to theturret framework by any convenient bracket means. Hydraulic fluid-isintroduced toeither side of the piston 341 by means of hydraulic pipes347, which carry fluid to the gimbal ring 345, and then via sealedswivel joints as shown to a chamber 348 above the piston 341 and to ahydraulic piper349 which leads to a like chamber 353 at the bottom ofthe cylinder 340.

If hydraulic pressure is removed, there is -a system provided tomanually control the gun in elevation. This system is amanually operatedseparate'hydraulic system. It has a manual pressure pump 54, connectedto the return side of the hydraulic system to pick up fluid; also acheck value 52 and accumulator 55, all to supply manual pump 323 withfluid to be circulated thereby. Added to this is a hydraulic no-backdevice 351 which is to keep fluid from flowing back from the elevatingcylinder 340 to the manual pump, while allowing fluid to be forced intothe elevating cylinder in either direction at any time (while theselector valve 322 is over in its manual position) by the manual pump323. This noback device 351 is in effect a dual check valve in whicheither check valve upon opening holds the other valve open at the sametime. The drawing in Fig. 4b shows the parts in a hypothetical positionin which fluid is being forced through the left-hand hydraulic pipe 352and returned to the pump through right-hand pipe 353. The pressureinpipe 352 has pushed back a ball 354 which is normally urged against itsvalve seat by a spring 355 and so acts as an ordinary check valve. Thesame pres sure inpipe 352 has forced a piston 356 over to its righthandposition as illustrated and as viewed in Fig. 4b. Thispiston 356 has twopins or rods which are attached as integral parts with the piston andall of which (piston 356 and the pins) move together. The result is thata right-hand ball 357, which is likewise spring biased against its valveseat to act as a check valve, is lifted from its seat and held open. Itis to be explained that piston 356 and its pins are so made as to allowboth check valves (right and left-hand, having balls 357 and 354,respectively) to remain closed when there is equal I pressure on bothsides of each. The result is that any back pressure developed in theelevation cylinder 340, e.g. due to vehicle traveling over roughterrain, will not motor the hand elevation pump 323. In other words, anyback pressure on the separate manually operated hydraulic system, whichmay develop in either hydraulic pipe 358 or 359 will *be checked at thehydraulic noback device 351, while any time pressure is applied by meansof the manual pump 323, it will be allowed to circulate fluid freely(whenever selector valve 322 is in its manual positionnot shown).

Elevation gyroscope unit 362 may be the same type of gyro unit astraverse gyro unit'312. The physical location determines its datum lineor line of reference so that otherwise both elevation and traverse gyrosare identical. The gyro unit 362 is connected electrically to thecontrol system by electrical lines 362a and 362k as indicated generallyin Fig. 4b of the drawings. The electrical circuit diagram is shown inFig. 5. The setting of a gunners control switch 365 to its on positioninitiates an electrical action whereby the gyroscopes are brought intooperation. After a specified time delay to enable the gyro rotor -toobtain operating speed, the entire system becomes operative.

A loaders safety switch 360 permits the loader to render the stabilizingsystem inactive in order to retrieve ammunition from the hull storagecompartment. The opening of switch 360 causes the deenergization of thesolenoid 275 of 'shut-ofi' valve 273 (Fig. 4a), and deenergization ofsolenoid 327 of clutch control valve 307 (Fig. 3), thereby removingpressure from the gun control system and placing the control in anautomatic travel lock condition.

A pressure gauge 361 which has a snubber (not shown) integral therewith,is located opposite the accumulator 55 in the manual hydraulic system toshow this systems pressure.

Fig. 5 is an electrical circuit diagram which shows the inter-relationof the various electrically actuated elements in the system. Theelectrical circuit, being that of a tank, is a DC. one wire type ofsystem in which the positive D'.C supply is connected to a single wire390 which directly supplies two branch circuits. There is a fuse 391 ineach of these branches. These fuses may be an appropriate ratingmechanical type of circuit breaker if desired. A wire 392 is connectedto the positive wire 390 via one of the fuses 391 and leads to one sideof the control switch 365 which is located in the gunners control tmitadjacent to his control handles 314 (Fig. 4b). When this control switchis closed, a common circuit wir'e 393 is energized. Branching from thiscommon circuit wire 393 are a number of circuits for electrical devicesamong which is a pilot or signal light 394 which will be energized toindicate that the control system has been turned on. Also connected tocommon circuit wire 393 is an elevation gyro rotor motor 395, the fieldwinding of which is indicated at 396. Since the gyro rotor motor 395 isdirectly connected to wire 393, and to the common ground circuit, itwill be energized as soon as the control switch 365 is closed and thegyro rotor will begin to be rotated up to its operating speed. Traversegyro rotor motor 397--which has its field winding 398 shown connected inseries in the same manner as with elevation gyro motor-As also connecteddirectly to wire 393 and to ground as illustrated, and will likewise beenergized upon closing of control switch 365. Elevation pick-off motor399 and traverse pick-off motor 400 are similarly directly connected towire 393 and will be energized as soon as control switch 365 is closed.The completion of each circuit for the elements just recited is made bya common ground circuit in the usual manner for a DC. system of thissort and such ground connection is illustrated in a functional manner bya ground connection symbol.

There is a thermal 'delay switch 405 which is of a type having a pair ofcontacts that are closed after a predetermined time delay from the timethat a heating element 406 is energized. This time delay switch405 hastwo resistors 407 and 408 connected in series with its heating element496. These resistors are shown asvariable merely for the purpose ofadjustment. Arela'y 409 is connected toone of the contracts of thermaldelay 9 switch 405 for -actuation thereby'when its contacts are closed.This relay controls three circuits as shown which are as follows:

One circuit is that of the control coils 404 and 378 for elevation andtraverse primary control valves 320 and 296 respectively (Figs. 4b and4a), which includes wire 410 connected to the right-hand fuse 391 (asviewed in Fig. 5) and to a normally open pair of contacts 411 of relay409. The remainder of this circuit will be discussed in more detailbelow.

The second circuit is that of the various control solenoids and includesa wire 412 which is directly connected to common circuit wire 393 and tonormally open contacts 413 of the above relay 409.

' The third circuit includes normally closed contacts 414 of relay 409.The purpose of this circuit is to insert resistor 407 into a seriescircuit including heating element 406 of thermal delay switch 405. So,when relay 409 has been actuated, contacts 414 will be opened andresistor 407 will act to reduce the current flow through the heatingelement 406 to a lowerlevel which will be sufficient to maintainactuation of thermal delay switch 405 without overheating, and therebypermitting quicker deactuation. The purpose of delay switch 405 is togive a sufficient time delay before energization of the first and secondcircuits mentioned above in order to allow the gyro rotor motors toreach approximately 60% of their final speed.

The first circuit controlled by relay 409 includes wire 417, which isconnected to contacts 413 and leads to the loaders safety switch 360.Then the circuit continues via wire 418, which is part of a commoncircuit for the solenoid 327 of hydraulic clutch valve 307, solenoid 275of the system shut-off valve 273, a traverse gyro caging solenoid 419,an elevation gyro caging solenoid 420, and a traverse tracking motor 421which has two series fields 422 and 423 for reversible operation. Aseparate circuit for each of these elements is completed by a groundconnection as clearly shown in the drawing.

The oil level and temperature responsive switch 376 is connected in acircuit common to both solenoids 275 and 327.. The purpose is to obviateany damage to the hydraulic system if there is insuflicient hydraulicfluid or if its temperature is too high for proper circulation. 'It(switch 376) may be any suitable type of switch which will be responsiveto both temperature and to the level of the hydraulic fluid. Theresponses are set to open the circuits of clutch valve solenoid 327 andsystem shut-off valve solenoid 275 if the hydraulic fluid level fallstoo low for safe operation or if the temperature of this fluid is toohigh for safe operation of the system.

There are resistors 426 which are connected in series with each of theelevation and traverse gyro caging solenoids 420 and 419 respectively.These resistors 426 however have short circuiting contacts 425 connectedacross each resistor 426. The caging solenoids 419, 420 and theresistors 426, as well as the contacts 425 are all elements of the knowngyro systems 312 and 362 (Figs. 4a and 4b) which are well known types ofgyro and pickoif units such as the type described in US. Patents Nos.2,521,379 and 2,464,592 to Leathers et a1. and assigned "toInternational Business Machines. As described in these patents justmentioned the operation of the caging mechanism is such that, when thesolenoid is energized, the gyro will be uncaged. It is to be notedtherefore that the gyros will not be uncaged until after their rotorshave had time to get up to at least 60% of full speed as pointed outabove. The action of contacts 425 and resistors 426 is an auxiliary onewhich serves to reduce the current flow through the solenoids 420 and419 after the uncaging actionhas been completed. This allows a positiveand rapid uncaging action to be had without overheating the uncagingsolenoid windings during standby uncaged condition.

The elevation and the traverse tracking motors 137 .10 ar'1d4421 arenormally connected to the circuits leading to the gunners controlhandles 314 (Fig. 4b) which determines the positions of slidingcontactors 427 and 428. These sliding contactors may be the usual typefound intracking motor control circuits such as the type fully describedin the application, Serial No. 284,606, filed April 26, 1952, and act todetermine the direction and speedof their respective tracking motors 137and 421. There is a commanders over-ride switch 431 which isconveniently located on the commanders control unit 313 (Fig. 4a) andwhich is shown directly connected to the commonly energized wire 393 bywire 432. When the tank commander desires to take tracking control ofthe gun away from the gunner, he closes thisswitch 431 which energizes arelay 433 as well as a motor 434 in the commanders tracking motorcontrol unit. Actuation of the relay 433 shifts control of the trackingmotors 137 and 421 from the gunner to the commander so that the gunnerstracking control is no longer efiective. This shift is eflected by theaction of multiple contacts 436 of relay 433, which contacts aremechanically actuated by an armature 437, also of relay 433. Thecontacts are spring biased into the position illustrated and will assumethe opposite position when relay 433 is energized. Therefore, when relay433 is energized, the circuits for tracking motors 137 and 421 will beconnected to commanders sliding contactors 438 and 439 respectivelywhich are physically positioned by the commanders control handles 313(Fig. 4a) in generally the same manner as the gunners sliding contactors427 and 423 are positioned by the gunners control handles 314 .(Fig.4b). .The, commanderscontactors 438 and 439 .and break commutator drum440 which is the speed controlling element for both tracking motors 137and 421. A motor 441 is directly connected to common wire 393 so thatthe gunners control unit has its commutator drum 440 constantly drivenwhenever the system is energized by the gunners control switch 365. Themotor 434 on the other hand is only energized whenever the commandersover-ride switch 431 is closed.

It will be observed that there is a safety circuit for the benefit ofthe loader so that whenever he must make a trip between the turret andthe hull of the tank, he can be sure that no relative motion is going totake place while he is in danger of being seriously injured by suchrelative motion. This safety circuit is controlled by loaders switch 360which shuts off the hydraulic system and declutches the main hydraulicpump.

There are limit switches 442 in circuit with the elevation trackingmotor 137. One switch 442 is in the circult of each of the two fieldwindings 443 of the motor 137. The purpose of these limit switches 442is-to avoid tracking the gun in elevation positions higher or lower thanthe structural limitations of the gun mount will allow. Thephysicallocation of the switches 442 may be any convenient mounting which willaccomplish the desired results.

Operation The operation of the system of our invention may be summarizedwith primary reference to Figs. 3, 4a and 4b. Beginning withstabilization, it will be noted that the gun 44 (Fig. 2) is to bemaintained in a given position which will remain fixed with respect tothe earth regardless 'of the changes in attitude which the body of thetank may assume. Any tendency for the gun 44 to change its positionrelative to the earth will be sensed by 'one of the two gyroscopes 370and 371 (Fig. 2) or gyros 312 and 362 (Figs. 4a and 4b), and thehydraulic control system will be actuated by these gyroscopes in orderto cause the relative position between gun 44 and the hull of the tankupon which it is mounted, to change in such a way as to maintain theposition of gun 44 (relative to the earth) fixed. The operation will bedescribed with reference only to the system for maintaining gun 44 in aconstant elevation position since both the elevation and the traversecontrol systems are similar and a description of the operation of eitherone will apply to the other.

When the hydraulic system is in operation following the electric controlsystem having been turned on at the switch 365 (Fig. 4b) on the gunnerscontrol panel, and following the delay period for run up of the gyrorotors to speed, the solenoid 327 (Fig. 3) will be energized and "hencethe valve 3ii7 will be actuated to cause fluid under pressure, due tothe accumulator 363, to cause the clutch 282 to be engaged so that themain hydraulic system pump-281 will be driven by the tanks engine 280.At the same time, solenoid 275 (Fig. 4a) of the cut off valve 273 willbe energized and so the valve 273 will be opened to allow the hydraulicsystem to be energized. Therefore hydraulic pressure will be appliedover pipe 318 (Fig. 4b) to the central chambers of secondary controlvalve 321 and primary control valve 320, as well as to the piston foractuating automatic-manual selectro valve 322.

As described in detail above, there is a continuous alternate, cyclicenergization of the solenoids which position hydraulic valve 320 (Fig.4b) at a predetermined constant frequency in such a manner that thevalve 320 is being driven against first one of its stops and then theother for equal periods of time. Therefore, the secondary valve 321 isbeing correspondingly driven from one extreme position to the other atthe same frequency, and consequently hydraulic pressure is beingadmitted first to one side of the elevation piston 341 and then to theother side thereof at a given frequency. This series of hydraulic energypulses which are applied to the elevation cyllinder 340 to reversiblydrive its piston 341 in opposite directions, will obviously tend tocause the gun ai to be driven up and down in elevation at the samefrequency as these pulses of hydraulic energy. The frequency of thepulses of hydraulic energy is so chosen that the gun will not besubstantially displaced so long as the two pulses which make up anygiven cycle, are equal and opposite in their duration. The result willmerely be that of holding the gun 44 in a vibratory condition having aneutral or medium position which corresponds to the desired aiming pointof the gun44.

So long as the tank hull is in such a position that gun 44 has thedesired elevation, the gyroscope 362 (Fig. 4b) will control theswitching mechanism for the solenoids so that energization of thesolenoids that control valve 32th will be had in equal duration pulses,alternately, as was clearly described above. Therefore the vibratorymotion without any displacement, as just described, will be produced ingun 44.

However, should the hull of the tank change position due to roughterrain such as hills, or the like, the gyroscope 362 (Fig. 412) willsense this change of position and will correspondingly vary the durationof the energization of the coils which actuate the valve 320, byincreasing the length of time that one coil is energized and decreasingthe length of time the other coil is energized in any given cycle.Therefore, a difierential in the duration of the hydraulic pulses whichare produced in the elevation cylinder 340 will be set up and thisdifferential will cause a displacement of the piston 341 Within thecylinder 34?; in-the required manner to change the elevation of the gun44 relative to the hull of the tank upon which it is'niounted, so thatthe gun elevation will not change relative to the earth. This istheusual operation of a stabilization system as controlled by agyroscope; however, it will be noted that our system enables 'theinertia .of =the gun 4410 work with the stabilization failure ofhydraulic pressure.

eflfect rather than against the same. This is due to the fioating actionwhich was described above.

error signal, so that the hydraulic system will act to reposition gun Min a manner as just described with regard to stabilization.

There is also a manual hydraulic system for controlling the position ofthe gun 44 in case the stabilization or automatic control system is notin operation due to a This manual system is simply comprised of amechanical hydraulic pump 323 which may be manually operated in onedirection or the other to circulate hydraulic fluid in such a way as toreposition the piston 34 1 Within its cylinder 340'. This may beaccomplished when the automatic system is not operating because thechange-over valve 322 will bepositioned (by its spring) to the left, asviewed in Fig. 4b, and therefore the hydraulic lines 359 and 358 fromthe manual pump 323 will be connected to the lines 347 which lead to theelevation cylinder 3'40.

While we have described a specific embodiment of our invention, it is tobe taken as illustrative only and in no way as limiting our invention.

We claim:

1. In a hydraulic control system for positioning a body in traverseincluding a primary control valve for determining the flow of hydraulicfluid from a source of fluid under pressure to a plurality of controlchannels, a secondary control valve for receiving the flow of fluid insaid control channels and amplifying the same, a reversible hydraulicmotor having two pressure lines fed by said secondary control valve, amanual pump having a pair of normally closed hydraulic lines connectingthe same with said motor, and hydraulic pressure operated means forby-pa'ssing fluid between said pressure lines and for opening saidnormally closed hydraulic lines between said manual pump and said motorwhen the system pressure falls below a predetermined minimum.

2. In combination with a hydraulic cylinder and piston arranged to beconnected to a gun and its supporting body for variably elevating thegun by varying the volume of liquid in the cylinder from one side of thepiston to the other, said piston having equal areas on both sidessubject to pressure; an hydraulically controlled valve for varying thevolume of liquid in said cylinder, pressure lines connecting said valveand said cylinder, an electrically controlled valve for controlling theactuation of said hydraulically controlled valve, manual pump meanshaving a pair of normally closed hydraulic lines connecting the samewith said cylinder, gyroscopic means including an electric circuit forcontrolling said electrically controlled valve in order to automaticallycontrol said cylinder and piston, and hydraulic pressure operated meansfor bypassing fiuid between said pressure lines and for opening saidnormally closed hydraulic lines between said-manual pump and said motorwhen the system pressure falls below a predetermined minimum.

3. In a hydraulic control system for positioning a body in traverseincluding a primary control valve for determining the flow of hydraulicfluid from-a source of fluid under pressure to a plurality of controlchannels, a secondary control valve for receiving the flow of fluid insaid control channels and amplifying the same, a reversible hydraulicmotor having two pressure lines fed by said secondary control valve, amanual pump having a pair of normally closed hydraulic lines connectingthe same with said motor, an hydraulic pressure operated valve means, aspring means adapted to bias said valve means to open or by-passposition for by-passing fluid between said pressure lines and foropening said normally closed hy- 13 draulic lines between said manualpump and said motor when the system pressure falls below a predeterminedminimum, and a valve means face subject to system pressure whereby saidvalve means is held closed against the pressure of said spring means solong as system pressure exceeds the pressure of said spring means.

4. In a hydraulic control ystem for positioning a body in traverseincluding a primary control valve for determining the flow of hydraulicfluid from a source of fluid under pressure to a plurality of controlchannels, a secondary control valve for receiving the flow of fluid insaid control channels and amplifying the same, a re versible hydraulicmotor having two pressure lines fed by said secondary control valve, amanual pump having a pair of normally closed hydraulic lines connectingthe same with said motor, a plurality of hydraulic pressure operatedvalves, spring means adapted to bias said valves to open or by-passposition for by-passing fluid between said pressure lines and foropening said normally closed hydraulic lines between said manual pumpand said motor when the system pressure falls below a predeterminedminimum, and a hydraulic pressure responsive piston having a facesubject to system pressure associated with said valves to hold the sameclosed against the pressure of said spring means so long as systempressure exceeds the pressure of said spring means.

5. In combination with a hydraulic cylinder and piston arranged to beconnected to a gun and its supporting body for variably elevating thegun by varying the volume of liquid in the cylinder from one side of thepiston to the other, said piston having equal areas on both sidessubject to pressure; an hydraulically controlled valve for varying thevolume of liquid in said cylinder, pressure lines connecting said valveand said cylinder, an electrically controlled valve for controlling theactuation of said hydraulically controlled valve, manual pump meanshaving a pair of normally closed hydraulic lines connecting the samewith said cylinder, gyroscopic means including an electric circuit forcontrolling said electrically controlled valve in order to automaticallycontrol said cylinder and piston, hydraulic pressure operated changeovervalve means for by-passing fluid between said pressure lines and foropening said normally'closed hy- References Cited in the file of thispatent UNITED STATES PATENTS 2,311,964 Parsons Feb. 23, 1943 2,388,010Pohl Oct. 30, 1945 2,425,433 Linderoth Aug; 12, 1947 2,445,765 Dawson etal July 27, 1948 2,457,242. Knowlton Dec. 28, 1948 2,532,334 -Rhyne eta1 Dec. 5, 1950 2,569,571 Newell et a1 Oct. 2, 1951 2,591,800 GardinerApr. 8, 1952 2,614,390 Poitras et a1 Oct. 21, 1952 2,655,838 'Ernst eta1. Oct. 20, 1953 2,660,793. Holschuh et a1 Dec. 1, 1953 2,663,995 Priceet al Dec. 29, 1953 2,679,138 Kane May 25, 1954 2,681,116 Treseder June15, 1954 2,735,405 Hipple Feb. 21, 1956 2,766,587 Newell et al. Oct. 16,1956 2,766,731 Brandes et al Oct. 16, 1956 UNITED STATES PATENT OFFICECERTIFICATE or CoRRRCTIoN Patent No., 23 18 193 August 9, 1960 WardLeathers et al6 It is hereby certified that error appears in the printedspecification of the above numbered patent requiring correction and thatthe said Letters Patent should read as corrected below.

Column l line 52 for "hydraluic" read hydraulic column 3 line 54, for"inputs" read inputs column 7 line 41, for "value" read valve column 8.line 75,, for

"contracts" read contacts column 13, line 7 for "ystem" read systemcolumn 14, line 21 list of reference cited for the patent number"2,311,964" read 2 311 864 =--i ERNEST W. SWIDER mxxx 1 AttestingOflicer V v ARTHUR -W. CROCKER Acting Commissioner of Patents UNITEDSTATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent Noo 2,948,,193August 9 1960 Ward Leathers et al It is hereby certified that errorappears in the printed specification of the above numbered patentrequiring correction and that the said Letters Patent Should read ascorrected below.

Column 1 line 52,, for "hydraluic read hydraulic column 3 line 54 for"inputs" read inputs column 7 line 41, for "value" read valve column 8line 75 for "contracts" read contacts column 13 line 7 for ."ystem" readsystem column 14 line 21 list of reference cited for the patent. number"2,311,964" read 2 3l1 864 Signed and sealed this 4th day of April 1961.

(SEAL) Attest: ERNEST W. SWIDER XXXXQQQQX X ARTHUR w. CROCKER AttestingOflicer Acting Commissioner of Patents

